Modbus library for STM32 Microcontrollers

This is a fork of MODBUS-STM32-HAL-FreeRTOS from alejoseb . This is a more stripped down version that includes more modbus functions (reading read only coils and registers)

USART and USB-CDC Modbus RTU Master and Slave library for STM32 microcontrollers based on Cube HAL and FreeRTOS.

Includes a project for a Nucleo-P-WB55 project. Includes defines for other STM32 boards.

Documentation

To see more information about the libararys functions/inner workings see the documentation.

Documenattion includes:

Master and Slave configuration and thread/task description with a diagram

Characteristics:

Portable to any STM32 MCU supported by ST Cube HAL.
Portable to other Microcontrollers, like the Raspberry PI Pico, requiring little engineering effort.
Multithread-safe implementation based on FreeRTOS.
Multiple instances of Modbus (Master and/or Slave) can run concurrently in the same MCU, only limited by the number of available UART/USART of the MCU.
RS232 and RS485 compatible.
USART DMA support for high baudrates with idle-line detection.
USB-CDC RTU master and Slave support for F103 Bluepill board.

File structure

├── LICENSE
├── README.md
├── MODBUS_WB55_SLAVE_RTOS_DMA --> Project folder for the STM32WB55 Nucleo-P board, with freeRTOS, DMA and RS485 enabled.
├── MODBUS-LIB --> Library Folder
    ├── Inc
    │   └── Modbus.h 
    ├── Config
    │   └── ModbusConfigTemplate.h --> Configuration Template
    └── Src
        ├── Modbus.c 
        └── UARTCallback.c

How to use the examples

Examples provided for STM32CubeIDE Version: 1.8.0 https://www.st.com/en/development-tools/stm32cubeide.html.

Import the examples in the STM32Cube IDE from the system folder
Connect your NUCLEO board
Compile and start your debugging session!
If you need to adjust the Baud rate or any other parameter use the Cube-MX assistant (recommended). If you change the USART port you need to enable the interrupts for the selected USART. Check UARTCallback.c for more details.

Notes and Known issues :

The standard interrupt mode for Modbus RTU USART is suitable for 115200 bps or lower baud rates. For Higher baud rates---tested up to 2 Mbps---it is recommended to use the DMA mode. Check the corresponding examples. It will require extra configurations for the DMA channels in the Cube HAL.
The USB-CDC example supports only the Bluepill development board. It has not been validated with other development boards. To use this example, you need to activate USB-CDC in your ModbusConfig.h file.

How to port to your own MCU

Create a new project in STM32Cube IDE for your MCU
Enable FreeRTOS CMSIS_V2 in the middleware section of Cube-MX
Configure a USART and activate the global interrupt
If you are using the DMA mode for USART, configure the DMA requests for RX and TX
Configure the Preemption priority of USART interrupt to a lower priority (5 or a higher number for a standard configuration) than your FreeRTOS scheduler. This parameter is changed in the NVIC configuration pane.
Import the Modbus library folder (MODBUS-LIB) using drag-and-drop from your host operating system to your STM32Cube IDE project
When asked, choose link folders and files
Update the include paths in the project's properties to include the Inc folder of MODBUS-LIB folder
Create a ModbusConfig.h using the ModbusConfigTemplate.h and add it to your project in your include path
Instantiate a new global modbusHandler_t and follow the examples provided in the repository
Note: If your project uses the USART interrupt service for other purposes you have to modify the UARTCallback.c file accordingly

Recommended Modbus Master and Slave testing tools for Linux and Windows

r0tary/Modbus-STM32WB